For account administrators only.
You can see and manage the information of all the groups within your organization by clicking on the "Administer" button on top of the page and then on "Groups" in the list to the right.
There you may add, edit or delete groups one-by-one by using the green gear icons on the right. When you click on it you will find a list of all users within the group and also a list of all available users, you can move them one way or the other depending on your preferences, you can also change the group name there.
Remember to use group names that will make sense to everybody, since they will be referring to those groups when deciding where to share their videos. You can create a new group by writing its name on "New group name" and then clicking on "Add new"